The present invention relates to a slide valve for closing large gas pipes, in particular such pipes carrying dust-containing hot gases, of the type including a slide plate that can be displaced transverse to the gas pipe through a housing opening, between an open position outside the slide housing and a closed position inside the slide housing, which housing opening can be closed by a closing element.
A shutoff slide val ve of this type is known from German DT-AS No. 2,136,216. However, the slide structure suggested therein possesses only a single sealing arrangement and consequently it is suitable only for closing pressurized gas pipes. On the other hand, in the case of pressurized pipes, e.g. the pipes of blast furnaces operating by counterpressure principle, the above known shutoff slide valve would begin to leak after a short time and its sealing surfaces would then be destroyed by the sand-blast type effect of the dust-containing gas, which under certain circumstances flows out with the velocity of sound.
In order to close pressurized gas pipes of this type, e.g. the so-called gravity-feed pipes between the blast furnace and the dust collector of a blast furnace installation, fully encapsuled insertion-disk slide valves are thus used, which slide valves include a housing, a fixed sealing seat in the housing and a movable sealing seat in the housing. Such valves guarantee a perfect tightness, even in counterpressure operation, due to the fact that the slide plate is completely encapsuled and the sealing seats of the housing can also be pressed against the sealing rings of the slide plate.
However, encapsuled insertion-disk slide valves are associated with the disadvantages of very high weight, high cost and, finally, the entire displacement of the slide plate takes place in the interior of the housing, i.e. the slide plate cannot be seen from the outside. Dust and moisture in the interior of the housing necessarily lead to the formation of deposits. The replacement of packings or of entire sealing rings comprising the packings is a difficult and time consuming operation, since large openings must be freed on the housing hood or the entire hood must be removed laterally. This also requires extensive crane equipment.